DESCRIPTION: The principal investigator indicates that this renewal proposal focuses on the application of pericyclic reactions in new methodology for the synthesis of several important classes of carbocyclic and heterocyclic organic compounds. It is stated that part I describes the development of new methods for the synthesis of four-, five-, and six-membered ring systems. A new method for the synthesis of cyclobutanones is to be investigated, and new cycloadditions leading to five- and six-membered rings are to be developed based on the application of (trialkylsilyl)vinylketenes as four-carbon synthetic building blocks. The principal investigator notes that a new method for the synthesis of 2,4-cyclohexadienones is to be developed and employed as a key step in an efficient synthetic approach to an A-ring synthon for the antitumor agent taxol. It is indicated that part II of the proposal describes the further development of a general regiocontrolled annulation route to highly substituted aromatic and heteroaromatic compounds. The principal investigator notes that the application of this methodology to the total synthesis of biologically active natural products will be studied and that specific target compounds include the antibiotic phenalenone diterpene atrovenetin, the hypocholesterolemic antibiotic ascochlorin, and the antineoplastic diterpene taxmairin B and that in addition, the application of an intramolecular enyne cycloaddition strategy to the total synthesis of the tetracyclic furanophenalenone diterpene salvilenone will also be examined.